fs/jbd2/checkpoint.c

   1 /*
   2  * linux/fs/jbd2/checkpoint.c
   3  *
   4  * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
   5  *
   6  * Copyright 1999 Red Hat Software --- All Rights Reserved
   7  *
   8  * This file is part of the Linux kernel and is made available under
   9  * the terms of the GNU General Public License, version 2, or at your
  10  * option, any later version, incorporated herein by reference.
  11  *
  12  * Checkpoint routines for the generic filesystem journaling code.
  13  * Part of the ext2fs journaling system.
  14  *
  15  * Checkpointing is the process of ensuring that a section of the log is
  16  * committed fully to disk, so that that portion of the log can be
  17  * reused.
  18  */
  19
  20 #include <linux/time.h>
  21 #include <linux/fs.h>
  22 #include <linux/jbd2.h>
  23 #include <linux/marker.h>
  24 #include <linux/errno.h>
  25 #include <linux/slab.h>
  26
  27 /*
  28  * Unlink a buffer from a transaction checkpoint list.
  29  *
  30  * Called with j_list_lock held.
  31  */
  32 static inline void __buffer_unlink_first(struct journal_head *jh)
  33 {
  34         transaction_t *transaction = jh->b_cp_transaction;
  35
  36         jh->b_cpnext->b_cpprev = jh->b_cpprev;
  37         jh->b_cpprev->b_cpnext = jh->b_cpnext;
  38         if (transaction->t_checkpoint_list == jh) {
  39                 transaction->t_checkpoint_list = jh->b_cpnext;
  40                 if (transaction->t_checkpoint_list == jh)
  41                         transaction->t_checkpoint_list = NULL;
  42         }
  43 }
  44
  45 /*
  46  * Unlink a buffer from a transaction checkpoint(io) list.
  47  *
  48  * Called with j_list_lock held.
  49  */
  50 static inline void __buffer_unlink(struct journal_head *jh)
  51 {
  52         transaction_t *transaction = jh->b_cp_transaction;
  53
  54         __buffer_unlink_first(jh);
  55         if (transaction->t_checkpoint_io_list == jh) {
  56                 transaction->t_checkpoint_io_list = jh->b_cpnext;
  57                 if (transaction->t_checkpoint_io_list == jh)
  58                         transaction->t_checkpoint_io_list = NULL;
  59         }
  60 }
  61
  62 /*
  63  * Move a buffer from the checkpoint list to the checkpoint io list
  64  *
  65  * Called with j_list_lock held
  66  */
  67 static inline void __buffer_relink_io(struct journal_head *jh)
  68 {
  69         transaction_t *transaction = jh->b_cp_transaction;
  70
  71         __buffer_unlink_first(jh);
  72
  73         if (!transaction->t_checkpoint_io_list) {
  74                 jh->b_cpnext = jh->b_cpprev = jh;
  75         } else {
  76                 jh->b_cpnext = transaction->t_checkpoint_io_list;
  77                 jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
  78                 jh->b_cpprev->b_cpnext = jh;
  79                 jh->b_cpnext->b_cpprev = jh;
  80         }
  81         transaction->t_checkpoint_io_list = jh;
  82 }
  83
  84 /*
  85  * Try to release a checkpointed buffer from its transaction.
  86  * Returns 1 if we released it and 2 if we also released the
  87  * whole transaction.
  88  *
  89  * Requires j_list_lock
  90  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  91  */
  92 static int __try_to_free_cp_buf(struct journal_head *jh)
  93 {
  94         int ret = 0;
  95         struct buffer_head *bh = jh2bh(jh);
  96
  97         if (jh->b_jlist == BJ_None && !buffer_locked(bh) && !buffer_dirty(bh)) {
  98                 JBUFFER_TRACE(jh, "remove from checkpoint list");
  99                 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
 100                 jbd_unlock_bh_state(bh);
 101                 jbd2_journal_remove_journal_head(bh);
 102                 BUFFER_TRACE(bh, "release");
 103                 __brelse(bh);
 104         } else {
 105                 jbd_unlock_bh_state(bh);
 106         }
 107         return ret;
 108 }
 109
 110 /*
 111  * __jbd2_log_wait_for_space: wait until there is space in the journal.
 112  *
 113  * Called under j-state_lock *only*.  It will be unlocked if we have to wait
 114  * for a checkpoint to free up some space in the log.
 115  */
 116 void __jbd2_log_wait_for_space(journal_t *journal)
 117 {
 118         int nblocks;
 119         assert_spin_locked(&journal->j_state_lock);
 120
 121         nblocks = jbd_space_needed(journal);
 122         while (__jbd2_log_space_left(journal) < nblocks) {
 123                 if (journal->j_flags & JBD2_ABORT)
 124                         return;
 125                 spin_unlock(&journal->j_state_lock);
 126                 mutex_lock(&journal->j_checkpoint_mutex);
 127
 128                 /*
 129                  * Test again, another process may have checkpointed while we
 130                  * were waiting for the checkpoint lock. If there are no
 131                  * outstanding transactions there is nothing to checkpoint and
 132                  * we can't make progress. Abort the journal in this case.
 133                  */
 134                 spin_lock(&journal->j_state_lock);
 135                 spin_lock(&journal->j_list_lock);
 136                 nblocks = jbd_space_needed(journal);
 137                 if (__jbd2_log_space_left(journal) < nblocks) {
 138                         int chkpt = journal->j_checkpoint_transactions != NULL;
 139
 140                         spin_unlock(&journal->j_list_lock);
 141                         spin_unlock(&journal->j_state_lock);
 142                         if (chkpt) {
 143                                 jbd2_log_do_checkpoint(journal);
 144                         } else {
 145                                 printk(KERN_ERR "%s: no transactions\n",
 146                                        __func__);
 147                                 jbd2_journal_abort(journal, 0);
 148                         }
 149
 150                         spin_lock(&journal->j_state_lock);
 151                 } else {
 152                         spin_unlock(&journal->j_list_lock);
 153                 }
 154                 mutex_unlock(&journal->j_checkpoint_mutex);
 155         }
 156 }
 157
 158 /*
 159  * We were unable to perform jbd_trylock_bh_state() inside j_list_lock.
 160  * The caller must restart a list walk.  Wait for someone else to run
 161  * jbd_unlock_bh_state().
 162  */
 163 static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh)
 164         __releases(journal->j_list_lock)
 165 {
 166         get_bh(bh);
 167         spin_unlock(&journal->j_list_lock);
 168         jbd_lock_bh_state(bh);
 169         jbd_unlock_bh_state(bh);
 170         put_bh(bh);
 171 }
 172
 173 /*
 174  * Clean up transaction's list of buffers submitted for io.
 175  * We wait for any pending IO to complete and remove any clean
 176  * buffers. Note that we take the buffers in the opposite ordering
 177  * from the one in which they were submitted for IO.
 178  *
 179  * Called with j_list_lock held.
 180  */
 181 static void __wait_cp_io(journal_t *journal, transaction_t *transaction)
 182 {
 183         struct journal_head *jh;
 184         struct buffer_head *bh;
 185         tid_t this_tid;
 186         int released = 0;
 187
 188         this_tid = transaction->t_tid;
 189 restart:
 190         /* Did somebody clean up the transaction in the meanwhile? */
 191         if (journal->j_checkpoint_transactions != transaction ||
 192                         transaction->t_tid != this_tid)
 193                 return;
 194         while (!released && transaction->t_checkpoint_io_list) {
 195                 jh = transaction->t_checkpoint_io_list;
 196                 bh = jh2bh(jh);
 197                 if (!jbd_trylock_bh_state(bh)) {
 198                         jbd_sync_bh(journal, bh);
 199                         spin_lock(&journal->j_list_lock);
 200                         goto restart;
 201                 }
 202                 if (buffer_locked(bh)) {
 203                         atomic_inc(&bh->b_count);
 204                         spin_unlock(&journal->j_list_lock);
 205                         jbd_unlock_bh_state(bh);
 206                         wait_on_buffer(bh);
 207                         /* the journal_head may have gone by now */
 208                         BUFFER_TRACE(bh, "brelse");
 209                         __brelse(bh);
 210                         spin_lock(&journal->j_list_lock);
 211                         goto restart;
 212                 }
 213                 /*
 214                  * Now in whatever state the buffer currently is, we know that
 215                  * it has been written out and so we can drop it from the list
 216                  */
 217                 released = __jbd2_journal_remove_checkpoint(jh);
 218                 jbd_unlock_bh_state(bh);
 219                 jbd2_journal_remove_journal_head(bh);
 220                 __brelse(bh);
 221         }
 222 }
 223
 224 #define NR_BATCH        64
 225
 226 static void
 227 __flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
 228 {
 229         int i;
 230
 231         ll_rw_block(SWRITE, *batch_count, bhs);
 232         for (i = 0; i < *batch_count; i++) {
 233                 struct buffer_head *bh = bhs[i];
 234                 clear_buffer_jwrite(bh);
 235                 BUFFER_TRACE(bh, "brelse");
 236                 __brelse(bh);
 237         }
 238         *batch_count = 0;
 239 }
 240
 241 /*
 242  * Try to flush one buffer from the checkpoint list to disk.
 243  *
 244  * Return 1 if something happened which requires us to abort the current
 245  * scan of the checkpoint list.
 246  *
 247  * Called with j_list_lock held and drops it if 1 is returned
 248  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
 249  */
 250 static int __process_buffer(journal_t *journal, struct journal_head *jh,
 251                         struct buffer_head **bhs, int *batch_count,
 252                         transaction_t *transaction)
 253 {
 254         struct buffer_head *bh = jh2bh(jh);
 255         int ret = 0;
 256
 257         if (buffer_locked(bh)) {
 258                 atomic_inc(&bh->b_count);
 259                 spin_unlock(&journal->j_list_lock);
 260                 jbd_unlock_bh_state(bh);
 261                 wait_on_buffer(bh);
 262                 /* the journal_head may have gone by now */
 263                 BUFFER_TRACE(bh, "brelse");
 264                 __brelse(bh);
 265                 ret = 1;
 266         } else if (jh->b_transaction != NULL) {
 267                 transaction_t *t = jh->b_transaction;
 268                 tid_t tid = t->t_tid;
 269
 270                 transaction->t_chp_stats.cs_forced_to_close++;
 271                 spin_unlock(&journal->j_list_lock);
 272                 jbd_unlock_bh_state(bh);
 273                 jbd2_log_start_commit(journal, tid);
 274                 jbd2_log_wait_commit(journal, tid);
 275                 ret = 1;
 276         } else if (!buffer_dirty(bh)) {
 277                 J_ASSERT_JH(jh, !buffer_jbddirty(bh));
 278                 BUFFER_TRACE(bh, "remove from checkpoint");
 279                 __jbd2_journal_remove_checkpoint(jh);
 280                 spin_unlock(&journal->j_list_lock);
 281                 jbd_unlock_bh_state(bh);
 282                 jbd2_journal_remove_journal_head(bh);
 283                 __brelse(bh);
 284                 ret = 1;
 285         } else {
 286                 /*
 287                  * Important: we are about to write the buffer, and
 288                  * possibly block, while still holding the journal lock.
 289                  * We cannot afford to let the transaction logic start
 290                  * messing around with this buffer before we write it to
 291                  * disk, as that would break recoverability.
 292                  */
 293                 BUFFER_TRACE(bh, "queue");
 294                 get_bh(bh);
 295                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
 296                 set_buffer_jwrite(bh);
 297                 bhs[*batch_count] = bh;
 298                 __buffer_relink_io(jh);
 299                 jbd_unlock_bh_state(bh);
 300                 transaction->t_chp_stats.cs_written++;
 301                 (*batch_count)++;
 302                 if (*batch_count == NR_BATCH) {
 303                         spin_unlock(&journal->j_list_lock);
 304                         __flush_batch(journal, bhs, batch_count);
 305                         ret = 1;
 306                 }
 307         }
 308         return ret;
 309 }
 310
 311 /*
 312  * Perform an actual checkpoint. We take the first transaction on the
 313  * list of transactions to be checkpointed and send all its buffers
 314  * to disk. We submit larger chunks of data at once.
 315  *
 316  * The journal should be locked before calling this function.
 317  */
 318 int jbd2_log_do_checkpoint(journal_t *journal)
 319 {
 320         transaction_t *transaction;
 321         tid_t this_tid;
 322         int result;
 323
 324         jbd_debug(1, "Start checkpoint\n");
 325
 326         /*
 327          * First thing: if there are any transactions in the log which
 328          * don't need checkpointing, just eliminate them from the
 329          * journal straight away.
 330          */
 331         result = jbd2_cleanup_journal_tail(journal);
 332         trace_mark(jbd2_checkpoint, "dev %s need_checkpoint %d",
 333                    journal->j_devname, result);
 334         jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
 335         if (result <= 0)
 336                 return result;
 337
 338         /*
 339          * OK, we need to start writing disk blocks.  Take one transaction
 340          * and write it.
 341          */
 342         spin_lock(&journal->j_list_lock);
 343         if (!journal->j_checkpoint_transactions)
 344                 goto out;
 345         transaction = journal->j_checkpoint_transactions;
 346         if (transaction->t_chp_stats.cs_chp_time == 0)
 347                 transaction->t_chp_stats.cs_chp_time = jiffies;
 348         this_tid = transaction->t_tid;
 349 restart:
 350         /*
 351          * If someone cleaned up this transaction while we slept, we're
 352          * done (maybe it's a new transaction, but it fell at the same
 353          * address).
 354          */
 355         if (journal->j_checkpoint_transactions == transaction &&
 356                         transaction->t_tid == this_tid) {
 357                 int batch_count = 0;
 358                 struct buffer_head *bhs[NR_BATCH];
 359                 struct journal_head *jh;
 360                 int retry = 0;
 361
 362                 while (!retry && transaction->t_checkpoint_list) {
 363                         struct buffer_head *bh;
 364
 365                         jh = transaction->t_checkpoint_list;
 366                         bh = jh2bh(jh);
 367                         if (!jbd_trylock_bh_state(bh)) {
 368                                 jbd_sync_bh(journal, bh);
 369                                 retry = 1;
 370                                 break;
 371                         }
 372                         retry = __process_buffer(journal, jh, bhs, &batch_count,
 373                                                  transaction);
 374                         if (!retry && (need_resched() ||
 375                                 spin_needbreak(&journal->j_list_lock))) {
 376                                 spin_unlock(&journal->j_list_lock);
 377                                 retry = 1;
 378                                 break;
 379                         }
 380                 }
 381
 382                 if (batch_count) {
 383                         if (!retry) {
 384                                 spin_unlock(&journal->j_list_lock);
 385                                 retry = 1;
 386                         }
 387                         __flush_batch(journal, bhs, &batch_count);
 388                 }
 389
 390                 if (retry) {
 391                         spin_lock(&journal->j_list_lock);
 392                         goto restart;
 393                 }
 394                 /*
 395                  * Now we have cleaned up the first transaction's checkpoint
 396                  * list. Let's clean up the second one
 397                  */
 398                 __wait_cp_io(journal, transaction);
 399         }
 400 out:
 401         spin_unlock(&journal->j_list_lock);
 402         result = jbd2_cleanup_journal_tail(journal);
 403         if (result < 0)
 404                 return result;
 405         return 0;
 406 }
 407
 408 /*
 409  * Check the list of checkpoint transactions for the journal to see if
 410  * we have already got rid of any since the last update of the log tail
 411  * in the journal superblock.  If so, we can instantly roll the
 412  * superblock forward to remove those transactions from the log.
 413  *
 414  * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
 415  *
 416  * Called with the journal lock held.
 417  *
 418  * This is the only part of the journaling code which really needs to be
 419  * aware of transaction aborts.  Checkpointing involves writing to the
 420  * main filesystem area rather than to the journal, so it can proceed
 421  * even in abort state, but we must not update the journal superblock if
 422  * we have an abort error outstanding.
 423  */
 424
 425 int jbd2_cleanup_journal_tail(journal_t *journal)
 426 {
 427         transaction_t * transaction;
 428         tid_t           first_tid;
 429         unsigned long   blocknr, freed;
 430
 431         /* OK, work out the oldest transaction remaining in the log, and
 432          * the log block it starts at.
 433          *
 434          * If the log is now empty, we need to work out which is the
 435          * next transaction ID we will write, and where it will
 436          * start. */
 437
 438         spin_lock(&journal->j_state_lock);
 439         spin_lock(&journal->j_list_lock);
 440         transaction = journal->j_checkpoint_transactions;
 441         if (transaction) {
 442                 first_tid = transaction->t_tid;
 443                 blocknr = transaction->t_log_start;
 444         } else if ((transaction = journal->j_committing_transaction) != NULL) {
 445                 first_tid = transaction->t_tid;
 446                 blocknr = transaction->t_log_start;
 447         } else if ((transaction = journal->j_running_transaction) != NULL) {
 448                 first_tid = transaction->t_tid;
 449                 blocknr = journal->j_head;
 450         } else {
 451                 first_tid = journal->j_transaction_sequence;
 452                 blocknr = journal->j_head;
 453         }
 454         spin_unlock(&journal->j_list_lock);
 455         J_ASSERT(blocknr != 0);
 456
 457         /* If the oldest pinned transaction is at the tail of the log
 458            already then there's not much we can do right now. */
 459         if (journal->j_tail_sequence == first_tid) {
 460                 spin_unlock(&journal->j_state_lock);
 461                 return 1;
 462         }
 463
 464         /* OK, update the superblock to recover the freed space.
 465          * Physical blocks come first: have we wrapped beyond the end of
 466          * the log?  */
 467         freed = blocknr - journal->j_tail;
 468         if (blocknr < journal->j_tail)
 469                 freed = freed + journal->j_last - journal->j_first;
 470
 471         jbd_debug(1,
 472                   "Cleaning journal tail from %d to %d (offset %lu), "
 473                   "freeing %lu\n",
 474                   journal->j_tail_sequence, first_tid, blocknr, freed);
 475
 476         journal->j_free += freed;
 477         journal->j_tail_sequence = first_tid;
 478         journal->j_tail = blocknr;
 479         spin_unlock(&journal->j_state_lock);
 480         if (!(journal->j_flags & JBD2_ABORT))
 481                 jbd2_journal_update_superblock(journal, 1);
 482         return 0;
 483 }
 484
 485
 486 /* Checkpoint list management */
 487
 488 /*
 489  * journal_clean_one_cp_list
 490  *
 491  * Find all the written-back checkpoint buffers in the given list and release them.
 492  *
 493  * Called with the journal locked.
 494  * Called with j_list_lock held.
 495  * Returns number of bufers reaped (for debug)
 496  */
 497
 498 static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
 499 {
 500         struct journal_head *last_jh;
 501         struct journal_head *next_jh = jh;
 502         int ret, freed = 0;
 503
 504         *released = 0;
 505         if (!jh)
 506                 return 0;
 507
 508         last_jh = jh->b_cpprev;
 509         do {
 510                 jh = next_jh;
 511                 next_jh = jh->b_cpnext;
 512                 /* Use trylock because of the ranking */
 513                 if (jbd_trylock_bh_state(jh2bh(jh))) {
 514                         ret = __try_to_free_cp_buf(jh);
 515                         if (ret) {
 516                                 freed++;
 517                                 if (ret == 2) {
 518                                         *released = 1;
 519                                         return freed;
 520                                 }
 521                         }
 522                 }
 523                 /*
 524                  * This function only frees up some memory
 525                  * if possible so we dont have an obligation
 526                  * to finish processing. Bail out if preemption
 527                  * requested:
 528                  */
 529                 if (need_resched())
 530                         return freed;
 531         } while (jh != last_jh);
 532
 533         return freed;
 534 }
 535
 536 /*
 537  * journal_clean_checkpoint_list
 538  *
 539  * Find all the written-back checkpoint buffers in the journal and release them.
 540  *
 541  * Called with the journal locked.
 542  * Called with j_list_lock held.
 543  * Returns number of buffers reaped (for debug)
 544  */
 545
 546 int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
 547 {
 548         transaction_t *transaction, *last_transaction, *next_transaction;
 549         int ret = 0;
 550         int released;
 551
 552         transaction = journal->j_checkpoint_transactions;
 553         if (!transaction)
 554                 goto out;
 555
 556         last_transaction = transaction->t_cpprev;
 557         next_transaction = transaction;
 558         do {
 559                 transaction = next_transaction;
 560                 next_transaction = transaction->t_cpnext;
 561                 ret += journal_clean_one_cp_list(transaction->
 562                                 t_checkpoint_list, &released);
 563                 /*
 564                  * This function only frees up some memory if possible so we
 565                  * dont have an obligation to finish processing. Bail out if
 566                  * preemption requested:
 567                  */
 568                 if (need_resched())
 569                         goto out;
 570                 if (released)
 571                         continue;
 572                 /*
 573                  * It is essential that we are as careful as in the case of
 574                  * t_checkpoint_list with removing the buffer from the list as
 575                  * we can possibly see not yet submitted buffers on io_list
 576                  */
 577                 ret += journal_clean_one_cp_list(transaction->
 578                                 t_checkpoint_io_list, &released);
 579                 if (need_resched())
 580                         goto out;
 581         } while (transaction != last_transaction);
 582 out:
 583         return ret;
 584 }
 585
 586 /*
 587  * journal_remove_checkpoint: called after a buffer has been committed
 588  * to disk (either by being write-back flushed to disk, or being
 589  * committed to the log).
 590  *
 591  * We cannot safely clean a transaction out of the log until all of the
 592  * buffer updates committed in that transaction have safely been stored
 593  * elsewhere on disk.  To achieve this, all of the buffers in a
 594  * transaction need to be maintained on the transaction's checkpoint
 595  * lists until they have been rewritten, at which point this function is
 596  * called to remove the buffer from the existing transaction's
 597  * checkpoint lists.
 598  *
 599  * The function returns 1 if it frees the transaction, 0 otherwise.
 600  *
 601  * This function is called with the journal locked.
 602  * This function is called with j_list_lock held.
 603  * This function is called with jbd_lock_bh_state(jh2bh(jh))
 604  */
 605
 606 int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 607 {
 608         transaction_t *transaction;
 609         journal_t *journal;
 610         int ret = 0;
 611
 612         JBUFFER_TRACE(jh, "entry");
 613
 614         if ((transaction = jh->b_cp_transaction) == NULL) {
 615                 JBUFFER_TRACE(jh, "not on transaction");
 616                 goto out;
 617         }
 618         journal = transaction->t_journal;
 619
 620         __buffer_unlink(jh);
 621         jh->b_cp_transaction = NULL;
 622
 623         if (transaction->t_checkpoint_list != NULL ||
 624             transaction->t_checkpoint_io_list != NULL)
 625                 goto out;
 626         JBUFFER_TRACE(jh, "transaction has no more buffers");
 627
 628         /*
 629          * There is one special case to worry about: if we have just pulled the
 630          * buffer off a running or committing transaction's checkpoing list,
 631          * then even if the checkpoint list is empty, the transaction obviously
 632          * cannot be dropped!
 633          *
 634          * The locking here around t_state is a bit sleazy.
 635          * See the comment at the end of jbd2_journal_commit_transaction().
 636          */
 637         if (transaction->t_state != T_FINISHED) {
 638                 JBUFFER_TRACE(jh, "belongs to running/committing transaction");
 639                 goto out;
 640         }
 641
 642         /* OK, that was the last buffer for the transaction: we can now
 643            safely remove this transaction from the log */
 644
 645         __jbd2_journal_drop_transaction(journal, transaction);
 646
 647         /* Just in case anybody was waiting for more transactions to be
 648            checkpointed... */
 649         wake_up(&journal->j_wait_logspace);
 650         ret = 1;
 651 out:
 652         JBUFFER_TRACE(jh, "exit");
 653         return ret;
 654 }
 655
 656 /*
 657  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
 658  * list so that we know when it is safe to clean the transaction out of
 659  * the log.
 660  *
 661  * Called with the journal locked.
 662  * Called with j_list_lock held.
 663  */
 664 void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
 665                                transaction_t *transaction)
 666 {
 667         JBUFFER_TRACE(jh, "entry");
 668         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
 669         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 670
 671         jh->b_cp_transaction = transaction;
 672
 673         if (!transaction->t_checkpoint_list) {
 674                 jh->b_cpnext = jh->b_cpprev = jh;
 675         } else {
 676                 jh->b_cpnext = transaction->t_checkpoint_list;
 677                 jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
 678                 jh->b_cpprev->b_cpnext = jh;
 679                 jh->b_cpnext->b_cpprev = jh;
 680         }
 681         transaction->t_checkpoint_list = jh;
 682 }
 683
 684 /*
 685  * We've finished with this transaction structure: adios...
 686  *
 687  * The transaction must have no links except for the checkpoint by this
 688  * point.
 689  *
 690  * Called with the journal locked.
 691  * Called with j_list_lock held.
 692  */
 693
 694 void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 695 {
 696         assert_spin_locked(&journal->j_list_lock);
 697         if (transaction->t_cpnext) {
 698                 transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
 699                 transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
 700                 if (journal->j_checkpoint_transactions == transaction)
 701                         journal->j_checkpoint_transactions =
 702                                 transaction->t_cpnext;
 703                 if (journal->j_checkpoint_transactions == transaction)
 704                         journal->j_checkpoint_transactions = NULL;
 705         }
 706
 707         J_ASSERT(transaction->t_state == T_FINISHED);
 708         J_ASSERT(transaction->t_buffers == NULL);
 709         J_ASSERT(transaction->t_forget == NULL);
 710         J_ASSERT(transaction->t_iobuf_list == NULL);
 711         J_ASSERT(transaction->t_shadow_list == NULL);
 712         J_ASSERT(transaction->t_log_list == NULL);
 713         J_ASSERT(transaction->t_checkpoint_list == NULL);
 714         J_ASSERT(transaction->t_checkpoint_io_list == NULL);
 715         J_ASSERT(transaction->t_updates == 0);
 716         J_ASSERT(journal->j_committing_transaction != transaction);
 717         J_ASSERT(journal->j_running_transaction != transaction);
 718
 719         jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
 720         kfree(transaction);
 721 }